It's basically just badly rendered -- they have removed all depth clues (lighting obviously, but they've also used flat projection instead of perspective). Your brain fills it in by basically picking which side is in front. That in turn determines the direction you see it rotating.<p>It's completely random, and has nothing to do with left or right brain dominance; it's even easy to force it to switch to the other direction.
Here are some cool things about handedness.<p>We all 'know' that left-handers use their right brain and right-handers use their left brain. In one library book about handedness, the author had found studies about which parts of the brain are used by two groups of people, one left-handed and one right-handed.<p>For right-handers, it was about 95% left-brain, and 5% right-brain. However, for left-handers, there were three possibilities. It was about 60-65% right-brain, 20-30% left-brain, and the cortex for 5 or 10% of them.<p>I don't remember what they were measuring, but a third option for left-handers is interesting in itself. (It may have been a study about which eye is dominant based on what a left-hander would say, so those for whom the cortex functioned in a different way were grouped with left-handers?)<p>Another book says that in those people who 'hook' their wrist when they write (so their hand is actually lower than their wrist), they do it subconsciously because their wrong brain is being used. They are NOT meant to be using that hand as their brain is struggling to use the correct brain. So, if you're right-handed, and you hook, you might actually be right-brained and left-handed. And, if you're 'left-handed' but you hook when you write, you're actually a righty.<p>I thought about this a bit and noticed that with about 10% of people self-identifying as left-handed, the stats above might fit. If 3-5 percent of right-handers use their right-brain, maybe they 'hook' and are in fact natural left-handers ('fake righties'). And if 20-30% of left-handers are actually left-brained, then that's a few percent of the overall population who are actually right-handed ('fake lefties'). Those could also be 'hookers' who aren't actually using their natural hand.
This has been linkjacked to oblivion. And I have not seen any compelling argument for right/left brainness based on viewing this image. It's merely an illusion that plays with your depth perception from lack of contrast and depth cues (motion parallax maybe, if you're so inclined).<p>I believe this is the <i>original</i> source of the image.
<a href="http://www.procreo.jp/labo/labo13.html" rel="nofollow">http://www.procreo.jp/labo/labo13.html</a>
The author says nothing beyond it being a mysterious illusion.<p>The switching is as arbitrary as the coriolis effect. Try this thought experiment. Imagine instead of a woman, there was a perfect, black, sphere in the image. You couldn't tell if it was rotating at all. Now I add a protrusion to the "equator." Its length would vary in a sinusoidal fashion, and you could guess the ball is rotating, but still cannot reason it's direction. I can then successfully add protrusions such that it looks like a human and you wouldn't be able to tell; it's a simple lack of visual cues.<p>edit: my bad, not the coriolis effect. I was referring to the toilet-draining direction that is incorrectly attributed to the effect. The point is, given a little push in one direction, the water, or the image, would continue to rotate in that direction.
Either I'm so thoroughly one-side-brained that I can't comprehend any other perspective, or we're all simply getting confused over semantics. I see the woman turning to her right. Does anyone see otherwise? Whether you call that clockwise or counter-clockwise just depends upon whether you define the ceiling or the floor as the point of reference.
I discovered that you can easily switch the rotation by:<p>A. Covering almost all the image and focusing only in the lower feet.<p>- or -<p>B. Closing your eyes and trying to picture it rotating in the opposite direction. And then opening your eyes.
that image is cool and freaky. it keeps switching on me. i think it has to depend on what side of the brain you are using when you looking at the image.